SS vs PVC

ALH_4

The inner pipe of Viessmann's concentric vent is polypropylene. (attachment is an excerpt from the venting manual)

I have not seen an adapter from stainless vent to PVC outside diamter. Maybe Metal Fab or Pro Tech makes one. They do make adapters for the Vitodens. I believe Crown is specifying stainless vent on the Bimini.

-Andrew

Dave Yates (PAH)

Interesting conundrum

Lately, I've been hearing rumblings about the emerging controversy for utilizing PVC to vent hi-eff boilers. Funny that the PVC mfgrs haven't weighed in on this issue previously, but as someone said at AHR: "Follow the money."

OK, here's my own personal conundrum. We've been installing hi-eff furnaces (forgive me Father, for I have & continue to sin) since they first arrived on the scene. Never once had a PVC failure, but we sure took our lumps with the then new technology!

Got to thinking (yeah, I know whay you're thinking!) about furnaces and mod-con boilers & their differences where venting and exhaust temps are concerned. The fact is, furnaces no longer emit hot air at anywhere near the upper limits they once did or anywhere near those we can see with boilers. In both of their operations, we see exhaust temps somewhat elevated above the return air or water temps.

PVC is rated for 140 F. But, I'm wondering under what conditions? The 10' of head required per code to pass muster in DWV systems? In there a pressure/temp correlation and, if so, where the heck can I find the chart? I'd sure like to hear some words from the PVC folks regarding this potential liability issue.

Are the SS & alternate plastic venting folks full of hot air or is this a real issue?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Glen

and in BC

we are allowed ABS to vent furnaces. Must be sch 40 and not the lessor "cellular" type. but with regard to pressure/temp - if the system only sees inches wc of pressure - would this not overcome the temp max? Even if there is a stated or published max temp? just thinking out loud - good question!

[Deleted User]

Good questions, and MORE...

Dave, I have no answers for your questions, but have another to add to the mix. I've been told by people in the know that there is a good possibility that the chlorides from poly vinyl chlorides. when draining back from the exhaust system, are exposing the HXers on the Mo- Co's (HR's new moniker for them :-)) to elevated chlorides, which are a known failing point for SS...

Are we setting ourselves up for failure? If we use all SS venting systems for these MoCo's (sounds like something you'd hack up in the morning after a long night of hanging out in smoky bars talking about hydronics don't it?:-)) is the SS venting system going to have to be replaced at some point in the near future due to chloride attack?

If yes, then I guess that is something else that needs to be taken into consideration in the life cycle costing for these new appliances. And if that is the way it is, then so be it. I just don't like SUPRISES after the fact...

I guess we'd have to look across the pond where MoCO's have been around for a much longer trial period.

ME

hr

Dammed if you do dammed if you

don't!

I'd start venting with stainless tomorrow IF the manufactures allowed it in their installation instructions

What's missing from the PVC manufactures is their approval, or any testing, stateing that the product is suitable for venting by products of combustion.

Is temperature and pressure rateing enough to keep us out of "down the road' problems, ala Plexvent, etc?

However, clearences to combustiables with stainless becomes an issue. What, exactly is the flue temperature on Mo-Co when selecting vent materials.

I know there have been issues with chemicals leaching from PVC water mains in Kansas City, and these are cold water applications?

Going to be interesting, guess who is stuck in the middle. AGAIN!

We need to insist the PVC manufactures approve their products for venting applications, in my opinion.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Dave Yates (PAH)

How bout

Cocomo's? COndensing, almost CO free MOdulating

Cornfusing, ain't it!

Why oh why can't we just go with the flow and take up knitting for a hobby? Cursed with a restless inquisitive mind that won't rest.

18.5" of powder & counting(G).

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Constantin

All true...

... and presumably that's why some mod-con boiler manufacturers specify polypropylene piping instead of PVC for flue venting purposes. Yet others go up another step and use Al29 stainless. When to say "enough" really depends on the actual install and your need for belts and suspenders, I suppose.

hr

Is CPVC or polypropylene

listed for flue gas material?

I know some manufactures, Lochinvar, MZ, etc send a starter piece of CPVC, for a higher protection level but still my question is...

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Steve_35

Didn't The Beach Boys sing that song? Cocomo?

hr

Same question, Andrew

Does that material carry a listing for flue gas use?? TUV, UL, CPI, ASTM, Buehler, Buehler anybody

To me it looks like a higher rated plastic product, not necessarily a flue pipe, per say.


At least it has an outer layer for extra protection I suppose.


hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Dave Yates (PAH)

intriguing

My GlowCore instructions required a 10' piece of CPVC, but I couldn't "see" a temp diff when checked & that always had me wondering......

Then came my Revolution & SS to replace the failed GC.

Followed by a beta-test Opus & PVC

Followed by a Munchkin & PVC...

Soon to be?

I have two PVC routes for exhaust. One that's vertical through the roof (2+ stories tall) and a second one running under the garage floor to a horiz term. Switching between them to experiment was done. However, the vert will serve nicely for the solar chase(G) as that becomes a reality.

Somewhere somebody has done the testing on PVC and knows its limitations for exhaust temps. I've seen PVC drainage lines following building fires, so there's definately a limit(G). Odd thing about that, was seeing a warehouse fire aftermath where the PVC melted away on the fire side of a block wall and then acted as a conduit for the fire's hot gases on into the bathrooms. The lines were still in tact, but quite droopy from having hot gasses passing through them to the long-abandoned employee restrooms that hadn't been used for many years. You could see the pathway the hot gasses took to the fixtures where resistance to flow was less by the droop in the PVC lines. Must have been pretty darned hot gasses as the steel beams in the building expanded and compromised the structure beyond the point where rebuilding was feasible.

Definately a pressure/temp relationship & for flue gasses, there's very little pressure. I've been unable to locate any charts that deal with PVC and flue gasses. The 140 F rating is associated with water pressure and drainage systems. I'm hoping this issue isn't simply a smoke screen being used by those who promote other flue piping, but I'm also baffled & concerned by the lack of info available.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bob Harper

listed venting?

Is PVC listed as a vent material? If the PVC fails, who is going to stand behind it? What is the warranty period on the PVC and what limitations? Tested for positive vent pressures?

Now, ask these same questions of the AL29-4C mfrs. Listed? Yep, UL1738. Mfr to stand behind it? He sells it as venting so yes, he'll be in court. Definite stated warranty such as 10yrs. Seals tested against positive vent pressures and leaks.

So what's the difference? Cost! The stainless can cost as much as the unit.

I recommend you ask the stainless mfrs. for all the documentation they have on which mfrs. and models either approve or specify stainless over PVC. Then, armed with the facts, you present the choices to the client and let them choose.

My main point on these vent systems is that irregardless of which system you use, you should be testing for leaks with at least 2 methods. I use chemical smoke, soap bubbles, and a combustion analyzer when I mess with these vents, which honestly isn't too often.

Steve_35

> Is PVC listed as a vent material? If the PVC

> fails, who is going to stand behind it? What is

> the warranty period on the PVC and what

> limitations? Tested for positive vent

> pressures?

>

> Now, ask these same questions of

> the AL29-4C mfrs. Listed? Yep, UL1738. Mfr to

> stand behind it? He sells it as venting so yes,

> he'll be in court. Definite stated warranty such

> as 10yrs. Seals tested against positive vent

> pressures and leaks.

>

> So what's the

> difference? Cost! The stainless can cost as much

> as the unit.

>

> I recommend you ask the

> stainless mfrs. for all the documentation they

> have on which mfrs. and models either approve or

> specify stainless over PVC. Then, armed with the

> facts, you present the choices to the client and

> let them choose.

>

> My main point on these vent

> systems is that irregardless of which system you

> use, you should be testing for leaks with at

> least 2 methods. I use chemical smoke, soap

> bubbles, and a combustion analyzer when I mess

> with these vents, which honestly isn't too often.

Mark Hunt

Well I can say this


A couple years ago a customer of mine was getting ready to sell his 2 year old, 5400 sqft McMansion to build a 7400 sqft McMasnsion. He and his dad installed the pool heater that was provided by the pool company. Guess what they used for the vent........you guessed it....PVC.

The unit was SUPPOSED to be vented with SS AND in 4". They used a rubber Fernco to reduce from 4" to 3" and ran the PVC out the side of the pool house. They used it for at least one pool season. The pipe was slighly discolored near the boiler and on the first horizontal run it was "drooping" a bit. We changed it all to SS. Stack temps over 250 degrees when I tested it. I would have thought the PVC would fail immediately with those temps. Go figure.

Wait until the new power-vented water heaters come out. Can't wait to see how manufacturers will suggest venting them. We have been finding stack temps of over 500 degrees on the atmospheric units. Not sure how they will cool those gases down on the power-vented water heaters. Larger amounts of dilution air I guess. Wonder if they'll sound like F-16's going into after-burner?

Mark H

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

ALH_4

ANSI/CSA

I should have taken more from the manual. Maybe it's better not to take any of it out of context at all, but here is the paragraph preceding the one I posted above.

From the information I have from GAMA and the IGAC (through Viessmann dated Jan '05) which this thread has caused me to re-read, I am somewhat confused. It appears that the primary failure concerns are regarding incorrect installation and/or use of Cellcore ABS pipe which cracks much more easily than PVC. There is some anecdotal evidence of plastic vent cracked at the first elbow(50% of the installations checked), but they do not mention whether it was ABS or PVC. Likely it was ABS. Apparently ANSI has a table of maximum allowable temperatures for non-metallic vent material that lists the maximum for PVC as 158F and 210F for CPVC. I do not have a copy of this table. There is also a mention of an ANSI testing method for non-metallic venting systems. I apologize for not having these documents handy, but we have not had to worry because we have thus far only sold the Vitodens.

-Andrew

don_52

No Standard...

According to one manufacturer;

Should Plastic Pipe & Fittings Be Used to Vent Combustion Gasses?

Use of plastic pipe to vent combustion gasses produced by water and spaceheating equipment has become common practice among plumbers and builders. Some equipment manufacturers expressly recommend this practice.
Occasionally, XYZ Pipe is asked for its position on the use of plastic pipe and fitting products for this application.

Industry Standards

A variety of organizations produce standards for the construction industry. The best known of these organizations is the American Society for Testing and
Materials International (ASTM). ASTM standards are developed by committees of industry experts and approved by the ASTM organization through a rigorous consensus process. These standards specify dimensional, performance and test
requirements for various materials, including piping products. Manufacturers like XYZ Pipe produce products that conform to these published standards.
None of these standards addresses the use of plastic piping to vent combustion gases.

Equipment Manufacturers

Manufacturers produce a wide variety of gas-fired water and space heating equipment. These manufacturers may specify plastic piping for venting of combustion gases, citing these ASTM and other standards within their technical
literature:

• ASTM D 2241 Specification for PVC Pressure Rated Pipe
• ASTM D 1785 Specification for PVC Plastic Pipe, Schedules 40, 80 and 120.
• ASTM F 891 Specification for Coextruded PVC Plastic Pipe With a Cellular Core.
• ASTM F 441 Specification for CPVC Plastic Pipe, Schedules 40 and 80.
• ASTM D 2661 Specification for ABS Schedule 40 Plastic Drain, Waste and Vent Pipe and Fittings.
• ASTM D 2665 Specification for PVC Plastic Drain, Waste and Vent Pipe and Fittings.
• ASTM F 438 Specification for Socket Type CPVC Plastic Fittings, Schedule 40.
• ASTM D 3311 Specification for Drain, Waste and Vent Fitting Patterns.
• ASTM F 628 Specification for ABS Schedule 40 Plastic Drain, Waste and Vent Pipe with a Cellular Core.

Although these standards specify dimensional, performance and test requirements for plumbing and fluid handling applications, and are often used to refer to or describe a particular type of pipe, they do not address venting of
combustion gasses. References to these standards by water heater or space heating equipment manufacturers should not be viewed as acceptance or approval by the ASTM for these applications.

Conclusion

At present there is little data available on the safety or durability of plastic pipe products used to vent combustion gases. The ASTM has not addressed this application, and the available data is insufficient for the plastic pipe and fitting industry to develop consensus specifications or guidelines. Equipment manufacturers are most knowledgeable about their own products and are best equipped to determine how their gas-fired heating equipment should be vented.
Accordingly, XYZ Pipe recommends that inquiries about the suitability of plastic piping systems to vent combustion gasses be directed to the manufacturer of the water or space heating equipment being installed.

So there ya go, no standard, no ASTM,NFPA, nada, whatever
the equipment manufacturers site as a standard is done in
error, since there exists no "approved for use as" standard
by any standards body, doesn't help does it?

Sorry bout that

Steve_35

There is a NFPA reference

to the use of plastic pipe for venting.

From NFPA54-2002:
"10.4.2 Plastic Piping. Plastic piping used for venting equipment listed for use with such venting materials shall be approved."

Looks to me they're putting the ball squarely in the equipment manufacturer's lap.

Dave Yates (PAH)

Is this a joke?

> to the use of plastic pipe for venting.

>

> From

> NFPA54-2002: "10.4.2 Plastic Piping. Plastic

> piping used for venting equipment listed for use

> with such venting materials shall be

> approved."

>

> Looks to me they're putting the

> ball squarely in the equipment manufacturer's

> lap.





To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Dave Yates (PAH)

Is this a joke?

"At present there is little data available on the safety or durability of plastic pipe products used to vent combustion gases."

You gotta be kidding me! I hope that's an old document that dates back to the 1980's. The first PVC DV I installed was around 1979 when I installed a "scrubber" on my Borg-Warner gas-converted oil furnace to boost it from 78% to a 90+ model. Danged noisy piece of equipment, but it operated on the exact same principle as the Opus I'd see many years later. A T at the breech permitted the negative pressure created by the spray-venturi to draw flue gasses into the resevoir & then circulated the "captured" Btu's through a hydro-coil in the RA.

Meanwhile, PlexVent arrived as furnaces reached the limits for flue gas condensation.

A few years later, 90+ furnaces arrived and PVC has been used to vent since that time. That's probably two decades of utilizing PVC for flue exhaust. More than enought time for adequate testing.

No one knows? That's hard to believe. Man I hate opening cans and finding worms!

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

don_52

I wouldn't joke...

about something that serious Dave, I didn't put the
mfg'g name in there on purpose.

I'll email you the link, if this assertion is in error
I'd like to know myself.

YATTTA ( Yet another thing to think about - Clammy )

If there is an agreed upon standard (somewhere), screwed
into the sub-text of something else I've missed it.

This thread raised my brow, so I started looking, there's
a UL lab just north of here, maybe I'll give them a call.

Regards, db

Edit, Most / All appliance mfg's are at least "liability
conscience", one would think that their equipment would have to have been tested in it's recommended configuration somewhere?

Dave Yates (PAH)

Not you!

I didn't mean to imply you were joking. Rather, it was a bit of sarcasm regarding the published statement that (hopefully) should be outdated. Sure reads like something I'd expect from the early days of using PVC or ABS or any other plastic piping for flue exhaust.

I can't bring myself to believe manufacturers of heating appliances would have such a cavalier attitude where consumer safety is concerned. As Red Green would say: "We're all in this together".

Maybe this week one of them will read this post and point us in the direction of charts, graphs or other educational materials that can lay these concerns to rest.

Hoping it won't be as wishey-washey as the venting termination regs. There's another area where I wish there'd be some consensus between codes, AGA, and mfgrs. One says a foot under or to the side of a window is ho-kay, yet the four-foot rule supposedly governs here. How in the world inspectors ever decipher who is correct is beyond comprehension and often varies from one to the other and their mood.

All of which dances around the CO issue.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Steve_35

This makes no sense to me.

> consensus between codes, AGA, and mfgrs. One says

> a foot under or to the side of a window is

> ho-kay, yet the four-foot rule supposedly governs

> here. How in the world inspectors ever decipher

> who is correct is beyond comprehension and often

> varies from one to the other and their mood.


The requirements on this are pretty clear and make absolutely no sense. At least make no sense to me. From NFPA 54-2002:
"10.8.3 The vent terminal of a direct-vent appliance with an
input of 10,000 Btu/hr (3 kW) or less shall be located at least 6 in. (150 mm) from any air opening into a building, and such an appliance with an input over 10,000 Btu/hr (3 kW) but not over 50,000 Btu/hr (14.7 kW) shall be installed with a 9 in. (230 mm) vent termination clearance, and an appliance with an input over 50,000 Btu/hr (14.7 kW) shall have at least a 12 in. (300 mm) vent termination clearance."

So, you can have a 100,000 btuh input appliance vent 12" from a window if you direct vent it. The manufacturers we deal with have interpreted this to mean sealed combustion units. If you take air from within the building and have only the exhaust connected to the outside the clearance is 4' to an air opening? This, to me, makes no sense. How can taking combustion air from the outside change the clearance so dramatically?

ALH_4

CO

What I don't understand is that using stainless vent would rarely be a make or break issue cost-wise, especially if the manufacturer recommended it. Why even bother using a material that even has the possibility of having a problem, and even worse, appears not to be backed up by PVC manufacturers for that application. In my mind using PVC to vent is probably fine, but why tempt fate?....especially when failure means endangering the lives of the building occupants.

-Andrew

Steve_35

SS vs PVC

> What I don't understand is that using stainless

> vent would rarely be a make or break issue

> cost-wise, especially if the manufacturer

> recommended it. Why even bother using a material

> that even has the possibility of having a

> problem, and even worse, appears not to be backed

> up by PVC manufacturers for that application. In

> my mind using PVC to vent is probably fine, but

> why tempt fate?....especially when failure means

> endangering the lives of the building

> occupants.


In many of the applications we use SS isn't listed by the equipment manufacturer as an approved product. I don't know of any SS vent manufacturer that lists their product for direct contact with combustibles while PVC is listed by the equipment manufacturer as suitable for zero clearance.

Frankly, in the current litigious atmosphere I find it hard to believe that major manufacturers don't feel they're on VERY solid ground when recommending the usage of PVC for venting their equipment.

Mark Hunt

Valid point Andrew

yet I have never seen a failure on a PVC vent that was approved by the manufacturer. I will not say that it can't happen, but I have never found one.

Of course this brings us back to proper combustion adjustments. If a gas fired appliance is under-fired, low stack temps will cause flue gas condensation. On a standard atmospheric appliance, the flue will be gone in no time. There is a picture on HVAC-talk that shows a SS liner that completely rotted due to this.

And I have to wonder why I have not heard of any catostrophic failures of PVC drains failing due to the use of caustic drain cleaning solutions. Who knows what concoctions have been poured into PVC drains?

Consider, if you will, the early power vented water heaters. Vented with beefed-up dryer vent hose, yet the vent typically out lasts the water heater??

If all of the mod/con boilers had to be vented in SS, I wouldn't care. I would vent them in SS. But where is the proof that PVC is a bad choice for a venting material? I see a lot of supposition, yet no science to back it up.

I am not closed minded to this subject, I just need proof.

Mark H

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Mark Hunt

Depressurization


They are "estimating" the depressurization effect of the power vent + what ever else is in the house that could cause depressurization.

Not sure how they got that number though.

Mark H

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

don_52

Category IV allows...

Cat IV, 90+ Condensing allows for AL29-C Single wall or

CPVC, I think it's >/= 450*F With the caveat

"Tested With Appliance" ( by whom, doesn't say )

Exhaust pipe material shall be CPVC schedule 40 pipe per ASTM F441 standard, or AL29-4C stainless steel certified to the current edition of UL 1738 or ULC-S636. Model 200 only may use PVC schedule 40 pipe per ASTM D1785, or PVC-DWV pipe per ASTM D2665, or ABS-DWV pipe per ASTM D2661.


ACTIVE STANDARD: F441/F441M-02 Standard Specification for Chlorinated Poly(Vinyl Chloride) (CPVC) Plastic Pipe, Schedules 40 and 80.

It's also mentioned under the NFPA section Pitman9 mentioned.

Still doesn't address the other long term effects of the
nasty stuff, Hydrogen Chloride and such, seems there is
some movement to limit use or get rid of it altogether.
Most landfill sites the don't even want it it seems.

Got to go eat some more worms.

Timco

In UT we can use CPVC, PVC, and ABS.

T

Timco

Timco

Bob Harper

UL 1738

This std. does address the corrosion issue to some extent. It was based upon primary research done by Battelle Labs who was searching for an alloy suitable to condensing furnace HX. The AL29-4C was one of the best performers. It is 29% chromium and 4% molybdenum developed by Allegheny-Ludnum mills. It is very hard and difficult to work with.

I've used Pro-Tech's (Ventinox) Fas N Seal pipe with good results. They have a list of boilers & furnaces it is approved for along with the corresponding adapter you must order to attach it to the appliance. It usually incorporates a drain tee right at the appliance collar.

I suggest to contact Martin Walwra ( pronounced something like "vervola" at ProTech in Albany. He is the man who introduced stainless steel liners to North America and got UL to create their liner standards 1777 and helped with the 1738 std. You could also contact Bob Zimmerman at UL for guidance. You can also contact Lloyd Green at Heat Fab. I never mess with Z-Flex so I can't give you any contacts there.

HTH,

Bob Harper

code confusion

David, yes there is a lot of confusion btw where gas vent terminations are allowed. Basically, if a unit is power vented such as a Cat. IV furnace or water heater, the 4 ft rule applies.

Direct vent units that are atmospherically vented (thermosyphon) are the ones allowed in close proximity to windows and such because of the low velocity and rapid dispersion of gases. They are treated separately in the code under 503.2.3 Direct-vent; 503.2.4 Equipment with integral vents; mechanical draft systems 503.3.3

BTW, the section we are discussing on plastic versus ss is found in 503.4.1 plastic piping and 503.4.2 Special gas vents.

clammy

how did i get into this

Hey db how did i get into this yet another thing to think about clammy? peace

Mike T., Swampeast MO

The ratings I see printed on Schedule 40 PVC are all based on 73°F temperature. 220 psi @ 73°F for 3"; 330 psi @ 73° for 1½" and 2".

Did find the following from this link:

"THE MAXIMUM SERVICE TEMPERATURE FOR PVC IS 140°F"

@140°F the 73°F pressure rating is reduced to 0.22 of the original, so if 330psi 3", it would be good for 72.6 psi @ 140°F.

Will keep looking, but I find NOTHING anywhere regarding how to apply any of this to air at no pressure. Lots of problems with that. No added weight to induce sagging. No pressure to induce bulging. 190°F air passing through PVC in a 73° room may well never heat the PVC to anywhere near 190°F...

don_52

Sorry Sir..

Mr. Clammy,

It was something that you wrote in a post in the
past couple of weeks, stuck me funny at the time.

With all the thorny issues we all have to deal
with on a dailey basis the last thing we need
most days is more stuff to think about.

Actually you coined some web-slang, "yet another thing
to think about", hence the yattta or yatta.

No offense was intended and if any was taken
I offer my humble apologies.

Regards, db

Anna Conda

Now there's an idea. Natural wool is well known for its insulating properties... Could offer little knitted insulation sleeves for piping... extra charge for colour coordination with the house decor. Could be another value-added service? ^____^

Mike T., Swampeast MO

Some PVC properties

413°F melting point

188°F glass temperature (essentially means that below 188° it behaves like glass)

Between glass temperature (188°F) and melting "point" (413°F) it begins to behave less like glass and more like liquid as temperature increases.

At 185° it deforms with a 10 kilonewton (2,248 pound-force) "needle load".

Surely PVC has been tested with condensing boilers, furnaces and water heaters--after all it receives a "zero clearance" combustion rating.

Am still looking deeper...